The volume knob on iOS 6 adjusted its reflection as the device was tilted using data from the gyroscope and accelerometer. This sort of realism in UI was unheard of previously, but Apple had had a lot more planned for future versions of iOS.
Apple’s vision for realism in interfaces was finally seen with iOS 7, where UI elements lived in layers at different depths along the z-axis, and reacted to motion differently, creating a parallax effect where objects closer to the eye move faster than ones that are farther away.
Macworld takes an in-depth look at this parallax effect: ...
